Semiconductor devices including a wiring substrate and a semiconductor chip mounted on the wiring substrate are known. Examples of such semiconductor devices include a semiconductor device where a semiconductor chip is mounted on a wiring substrate that includes an insulating layer, a wiring layer formed on the insulating layer, and a solder resist layer formed on the insulating layer and including an opening that selectively exposes the wiring layer.
According to this semiconductor device, the wiring layer of the wiring substrate and a bump of the semiconductor chip are joined by solder provided in the opening, and an underfill resin fills in where the solder resist layer of the wiring substrate faces the semiconductor chip. (See, for example, Japanese Laid-open Patent Publication No. 2016-021482.)